The NASICON structure has been reported to consist of a three-dimensional framework built up from PO.sub.4 tetrahedra and MO.sub.6 octahedra, where M is a metal ion which has been incorporated into the NASICON framework. The PO.sub.4 and MO.sub.6 tetrahedra are believed to share vertices to form secondary building units of the general formula M.sub.2 (PO.sub.4).sub.3. These building units are reported to be stacked along the c-axis to form fairly large cavities that are interlinked to form tunnels. These tunnels are believed to contain sodium.
The NASICON phases initially attracted attention because of the high mobility of Na+ ions in the tunnels of the parent phase Na.sub.3 Zr.sub.2 Si.sub.2 PO.sub.12, giving rise to high ionic conductivity and use in fuel cells. P. Hagenmuller and W. Van Gool Solid Electrolytes Academic Press, New York (1978). The stability of the NASICON framework and its ability to form solid solutions containing a wide variety of elements has also been exploited in the preparation of zero thermal expansion coefficient (ZTEC) materials. A. El Jazouli et al. C.R.Acad.Sc.Paris t.300, Serie II, n.degree. 11, 1985, 493-496. More recently, the isostructural phases with copper substituted for sodium have been reported to be catalytically active for decomposition of alcohols. A. Serghini et al., J. Chem. Soc., Faraday Trans., 1991, 87,2487-2491.
For a discussion of synthesizing vanadium-containing NASICON materials, see A. Bermoussa et al., Journal of Solid State Chemistry 97, 314-318 (1992), and J. Gopalakrishnan et al., Chemistry of Materials, Vol. 4, No. 4, 745-747 (July/August 1992).
The material of this invention is a useful catalyst for upgrading organic feedstocks. The material promotes partial oxidation reactions, such as the reaction of n-C.sub.4 to form products less deeply oxidized than CO and CO.sub.2 (such as maleic anhydride, furan, and butadiene) at temperatures below 400.degree. C. The material also catalyzes the reaction of alkylaromatics, e.g., o-xylene, to aromatic oxygenates e.g., phthalic anhydride. Phthalic anhydride can be used in preparing alkyl, amino, and epoxy resins, as a flame retardant, rubber retarded, or as an ester for plasticizers and polyesters.